1. Technical Field
This disclosure pertains generally to flanged joints, and more specifically relates to leak detection at flanged joints.
2. Background Art
Flanged connectors have been used in a variety of different applications to produce gas-tight flanged joints. One known type of flanged joint 100 is shown in FIG. 1. The flanged joint 100 has two flanged connectors 110 and 120. First connector 110 includes a pipe 112 and a flange 114. Second connector 120 includes a pipe 122 and a flange 124 that mates with flange 114. The two flanges 114 and 124 are typically joined using a plurality of bolts, two of which are shown in FIG. 1 as 132 and 134. Bolts 132 and 134 pass through aligned holes in flanges 114 and 124, and corresponding nuts 142 and 144 are used to tighten the bolts and thus mate flanges 114 and 124 in a gas-tight manner to form a flanged joint. The coupling between flanges 114 and 124 is not shown because the manner in which the flanges are coupled to form a flanged joint is well-known in the art.
Flanged connectors are often used to distribute various liquids and gasses in pipelines and equipment that use the liquids and gasses. One example of an apparatus that uses flanged connectors is gas turbines that generate electricity from natural gas. In a typical gas turbine, there are a large number of burners that must each be supplied with natural gas. As a result, a gas turbine may have a large number of flanged connectors that form flanged joints.
Gas turbines require periodic maintenance. Maintaining a gas turbine often requires disassembling the turbine at the flanged connectors in order to clean or replace fuel screens, repair of breakdowns, periodic scheduled inspections, periodic scheduled maintenance, etc. When the flanged connectors are reassembled into a flanged joint, a check is typically made to make sure the flanged joint does not leak gas. Referring to FIG. 2, a method 200 represents a known way to perform gas leak detection after reassembling a flanged joint. Masking tape is wrapped around the flanges of a flange joint to enclosed the gap between flanges (step 210). A hole is then made in the masking tape (step 220), typically by pressing the point of a pen or pencil through the masking tape. The tip of a sniffer probe of a gas detector is then placed in or near the hole (step 230). If the flanged joint is leaking gas, the masking tape will contain the gas in the gap between the flanges so the sniffer probe can detect the gas.
The prior art method 200 for detecting gas leaks at a flanged joint is effective, but leads to problems later on when the flanged joint needs to be disassembled again, as shown in method 300 in FIG. 3. Before the flanged joint is disassembled, the masking tape must manually be removed from the flanges (step 310). The process of removing the masking tape is very time-consuming and tedious. Because the flanges are very hot when the turbine is operating, the masking tape becomes very brittle and the adhesive on the tape becomes baked-on. As a result, a service person for the gas turbine may spend 30 minutes or more removing the masking tape on each flanged joint. While removing the masking tape, small brittle pieces of the tape may fall between the flanges. Because the gas turbine is typically exhausted through large stacks, airflow to the stacks creates a slight vacuum that sucks any pieces of masking tape into the turbine. The service person disassembles the flanged joint (step 320). In the processing of disassembling the flange joint, any small piece of masking tape between the flanges may get sucked into the gas turbine. If the service person notices a piece of masking tape getting sucked into the turbine, further disassembly typically is required to locate and retrieve the piece of masking tape. If the service person does not notice a piece of masking tape getting sucked into the turbine, the service person may completely reassemble the turbine, then test it only to find that a burner is not operating correctly due to a blockage caused by the piece of masking tape. As a result, the service person will have to disassemble the gas turbine again to locate the blockage and remove it, greatly increasing the time to service the gas turbine. Without a way to perform gas leak detection of flanged joints in a way that does not cause the problems associated with the masking tape used in the prior art, service technicians of flanged joints will continue to spend excessive time dealing with the problems that arise from using the masking tape.